From: Jean-Luc Cooke <jlcooke@certainkey.com>
To: "David S. Miller" <davem@redhat.com>
Cc: root@chaos.analogic.com, adilger@clusterfs.com,
shemminger@osdl.org, alan@lxorguk.ukuu.org.uk, tytso@mit.edu,
netdev@oss.sgi.com, linux-kernel@vger.kernel.org
Subject: Re: [RFC] enhanced version of net_random()
Date: Fri, 20 Aug 2004 15:53:02 -0400 [thread overview]
Message-ID: <20040820195302.GK5806@certainkey.com> (raw)
In-Reply-To: <20040820124823.071ac1d9.davem@redhat.com>
If speed is what you want, and you want a period > 2^N.
Then a single get_rand_bytes() to fill a seed of a simple LFSR might do.
Seed value will be N+1 bits long.
Rochard's PRNG does not have a period > 2^32, that's for sure.
JLC
On Fri, Aug 20, 2004 at 12:48:23PM -0700, David S. Miller wrote:
> On Fri, 20 Aug 2004 15:22:09 -0400 (EDT)
> "Richard B. Johnson" <root@chaos.analogic.com> wrote:
>
> > The attached code will certainly work on Intel machines. It is
> > in the public domain, having been modified by myself to produce
> > a very long sequence...
>
> How long a period does it have? The one we're adding to the
> networking has one which is 2^88.
>
> > I wouldn't suggest converting it to 'C' because the rotation
> > takes many CPU instructions when one tries to do the test, shift,
> > and OR in 'C',
>
> You only need 2 'shifts' and an 'or' to do a rotate in C.
> No tests are needed.
next prev parent reply other threads:[~2004-08-20 20:01 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-12 17:48 [RFC] enhanced version of net_random() Stephen Hemminger
2004-08-12 19:48 ` David S. Miller
2004-08-13 18:51 ` Stephen Hemminger
2004-08-13 19:28 ` Andi Kleen
2004-08-16 6:27 ` David S. Miller
2004-08-12 20:02 ` Ben Greear
2004-08-20 17:59 ` Jean-Luc Cooke
2004-08-20 18:47 ` David S. Miller
2004-08-20 18:59 ` Andreas Dilger
2004-08-20 19:22 ` Richard B. Johnson
2004-08-20 19:48 ` David S. Miller
2004-08-20 19:53 ` Jean-Luc Cooke [this message]
2004-08-22 15:04 ` Andi Kleen
2004-08-23 17:05 ` Stephen Hemminger
2004-08-23 18:09 ` Richard B. Johnson
2004-08-20 21:24 ` Lee Revell
2004-08-20 23:55 ` Alan Cox
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